Limiting gun control to the mentally ill won't work — often we don't know they're crazy until they strike

Since the Newtown atrocity, a division is forming on gun control: people (including NYPD Commissioner Ray Kelly) who think the country should prevent mass murders by more tightly restricting access to guns in general, and people who think the country should prevent mass murders by keeping only the mentally ill from military-style artillery.

Unfortunately, the latter approach wont work.

Its obvious that mass shooters often have serious mental impairment. Jared Loughner had schizophrenia before he killed six people and wounded Congresswoman Gabby Giffords in Arizona two years ago.

Almost everyone who knew him at Virginia Tech was terrified of Seung-Hui Cho before he killed 32 people in 2007.

So keep them from getting guns, right?

Good idea, but easier said than done. Current law prohibits people who have been involuntarily institutionalized from getting weapons. But the system relies on self-reporting by gun buyers and spotty reporting by states. States, in turn, rely on spotty reporting by harried professionals in a patchwork health-care system.

And only one of the above shooters — Cho — should have been kept from a weapon under that mental-helath law, anyway. Loughner didnt get his diagnosis until after his murders. Holmes, now awaiting trial, doesnt have an official diagnosis yet.

Sure, the feds could mandate that all psychiatrists and family and emergency-room doctors immediately report anyone who could be psychotic to a national gun registry.

But thats a lot of people. Ask a cop how many "emotionally disturbed" people he sees on his shift.

It becomes even trickier when the alleged mental illness isnt schizophrenia.

Early reports indicate that Adam Lanza, the Newtown shooter, had Aspergers syndrome, a form of autism. People with Aspergers often obsess over one or two things and have difficulty relating to other people — but they are no more likely to be violent than anyone else.

Still, though, if Lanza indeed had Aspergers, why not just take away automatic and semiautomatic weapons from all people with Aspergers, and other "mental illnesses," too, just in case?

The problem is that beyond a brain disorder like schizophrenia, mental health is hardly a science.

Diagnoses are often wrong — or they dont mean much, anyway. Earlier this year, Benjamin Nugent, creative-writing director at Southern New Hampshire University, wrote that as a teen in the 1990s, he starred in an education video about living with Aspergers. But once he found a niche, he was fine. "I wasnt that awkward or isolated anymore."

Remember when everyone had attention-deficit disorder back in the 80s — but it turned out that the main problem was that its hard for a 5-year-old to sit still for 12 hours? Aspergers is the new faddy diagnosis — partly because not everyone is cut out to be a bubbly "event planner."

The mental-health profession could rely on family reporting of a persons mental state and whether its changed or not over the years.

Buts its unclear why having the federal government compile a list of millions of people who might have schizophrenia, depression, Aspergers or other ills — and then constantly updating that list based on family, friend and caregiver informants information — is any less a violation of civil liberties than banning military-assault weapons and ammunition.

When someone intones in TV that we need to keep the "mentally ill" from weapons, ask yourself:

* Should a shy 14-year-old boy be able to go deer hunting with dad?

* Should a single mom who lives on a farm, and whos been taking antidepressants for two decades, be allowed to have a weapon to protect her family from intruders?

* Should a 70-year old man whos showing signs of forgetting things still be allowed to keep the guns that hes had for 50 years?

* Should a vet having therapy for post-traumatic stress disorder have his gun confiscated?

Moreover, if a parent knows that bringing his kid to see a psychiatrist could prevent that kid from, say, a career in law enforcement in a decades time, he might refrain from getting his kid the help he needs.

Finally, going with the mental-health approach still would require gun-show and other "dealers" to perform background checks — a loophole-closing that the gun lobby has historically opposed.

Better mental-health care is a good idea — but expecting the health-care profession to be the first line of defense against madmen with guns is not sufficient. When firearms of mass destruction are too easy to get, the mentally ill inevitably will get their hands on them, too.